Specific Heat of LiquidHe3/He4Mixtures near the Junction of the

Abstract

The specific heat of liquid He /He mixtures has been measured at saturated vapor pressure for eight values of the He mole fraction~in the range 0. 53 «x «0.73 at temperatures from -0.6 tol. 4 K. For purposes of comparison, the specific heat of pure liquid He has also been measured under similar conditions. The measured specific heat, obtained with a calorimeter almost completely full of liquid, has been corrected to yield the specific heat of the liquid cJ. "at constant pressure and mole fraction. For the mixtures, the correction required was everywhere & 17&. To a resolution in temperature which varies from 0.1 to 3 m'K from one value of x to another, the specific heat at the A. peak appears to be finite, continuous, and cusped. Both the A. peak and the discontinuity in cJ, "as the system goes from the two-liquid-phase region to the one-liquid-phase region tend to disappear as the junction of phase boundaries is approached.

Phase diagram and concentration susceptibility of 3He-4He mixtures near the tricritical point

“…Other studies of (a~b/aX)-r have been reported by Goellner et al, t also based on vapor pressure measurements; by Alvesalo et al 3 from heat capacity measurements; by Leiderer et al 4 from light scattering; and by Ryschkewitsch et al, 5 who measured the vertical concentration gradient.…”

Specific heat near the lambda point in 4He and 3He-4He mixtures: Test of universality of the critical exponent and the amplitude ratio, and observation of the critical-tricritical crossover effect

“…7 On the other hand, at'the tricritical point the values of a6 and a~ are 0.5 according to the specific heat measurements of Alvesalo et al 8 and to theory. 9 It is of interest to study how the characteristics of Cp,~ are modified from critical to tricritical behavior, that is, from a ~}-0 to o~g )= 0.5.…”

THERMODYNAMIC PROPERTIES OF LIQUID [sup 3]He-[sup 4]He MIXTURES BETWEEN 0.15 K AND 1.5 K

“…The specific heats are linear with x at a given temperature in the two-phase region [4,11]. Therefore, the specific heat at a given x and T can be written as:…”

“…The deviation terms C r,I (x,T) and C r,II (x,T) are calculated from fits to available mixture data. The primary sources of data are Alvesalo et al [11] and de Bruyn Ouboter et al [15], which are the only sources at values of x greater than about 0.2. Radebaugh's calculated specific heats [1] are also used, albeit only at low 3 He concentrations, where they are expected to be good.…”

“…C 2φ,t and ∂C 2φ /∂x were fitted to polynomial functions of temperature using experimental specific heat data (primarily that of Alvesalo et al [11], available only at T > 0.55 K) and specific heats inferred from the dilute- 3 He-mixture model and pure 3 He data of Kuerten et al [2] at T < 0.15 K. (At temperatures below 0.15 K, the concentrated phase is more than 99.9% 3 He [12] and can be approximated to be pure 3 He.) The fit was interpolated between these two limits.…”